1. Field of the Invention
The present invention relates to an electrical living body stimulation signal waveform generation device and an electrical living body stimulation device, which give an electrical stimulus to a living body and thereby effectively offer muscle training, relaxation, figure improvement, muscle pain healing, fatigue recovery treatment, and the like.
2. Description of the Related Art
It is a widely known practice that electrodes (pads) are brought into contact with the surface of a living body and electrical pulse waves and electrical sine waves are given thereto, whereby an electrical stimulus is given to a muscle causing the muscle to be activated and relaxed. Electrotherapy devices and electrical health equipment, each of which uses such effects of the electrical stimulus, are put into practical use. Depending on the purpose, such devices and equipment are used in various ways such as for muscle stimulation, muscle rehabilitation, muscle training, figure improvement, relaxation, and further, treatments for muscle pain, stiffness, numbness, lumbago and fatigue recovery.
A large number of living body stimulation devices, each of which is based on such an electrical stimulus as described above, use low-frequency pulses. A low-frequency pulse current is allowed to flow between electrodes arranged on two or more spots on the living body, the stimulus is given to the muscle between the electrodes, and the muscle is repeatedly contracted and relaxed. In such a way, the bloodstream of the muscle is accelerated and physical effects such as shoulder tapping, massage therapy, and muscle training can be obtained.
As the low-frequency pulses of the electrotherapy device or the like, pulse waves of several hertz to several ten hertz are used. The voltage intensity of the pulses, the width of the pulses, the ON/OFF interval of the pulses thus generated, and the like are changed and are combined with one another, whereby a pulse waveform, which corresponds to a particular purpose such as shoulder tapping, muscle tone-up, and relaxation, is formed. For example, low-frequency therapy devices or the like which are commercially available at present, generate reference pulses with a pulse width from 0.2 milliseconds to several milliseconds at a pulse voltage from 10V to 20V. Then, in the shoulder tapping mode, the generation interval of the reference pulses is changed from several milliseconds to several seconds in response to preferences of a user, and a desired shoulder tapping effect is obtained. Moreover, in modes such as the massage effect and the relaxation effect, ten to several-ten groups of the above-described reference pulses are repeatedly turned on and off with cycles ranging from one to several seconds, whereby a manual massage effect is obtained.
Although definitions of a low frequency and a high frequency are not definite, low frequency generally stands for a frequency of less than 20 kHz in this industrial field (electrotherapy field), and high frequency stands for a frequency of 20 kHz or more. Moreover, in the case of including the concept of a medium frequency, a frequency of less than 1 kHz is defined as the low frequency, a frequency of 1 kHz to less than 10 kHz is defined as the medium frequency, and a frequency of 10 kHz or more is defined as the high frequency. When the low-frequency pulses are given to the muscle, the muscle is stimulated and contracted. However, when such pulse waves are thereafter paused, the muscle starts to relax. In the shoulder tapping mode or the like, low-frequency pulses of several hertz to several ten hertz are used, and every time each of the low-frequency pulses is given, the muscle is relaxed, and there is brought about a shoulder tapping effect with a feeling like “tap, tap . . . .” Moreover, when the frequency of the low-frequency pulses is increased, and where, before the muscle starts to be relaxed, the next pulse is continuously given without any interval, then the contracted state of the muscle is held. Thereafter, an interval state thereof where the pulses are paused is brought about, whereby the muscle turns to a relaxed state, and an effect that the muscle is massaged slowly is created.
In this type of low-frequency pulse therapy device, rectangular pulses are usually used. Therefore, owing to the pulse stimulus caused by a sudden voltage change, there occurs a stimulation feeling like prickling (or sticking, shaking). A variety of proposals have been made in order to solve such an uncomfortable feeling. For example, a method of absorbing the stimulation feeling, by alternately changing positive and negative polarities of the low-frequency rectangular pulses to be given, is put into practical use in many electrical stimulation therapy devices. Moreover, by using the fact that a stimulus given to a living body by sine waves is generally weaker in comparison with that given thereto by the rectangular pulse waves, sine wave components are mixed into the rectangular pulses. Methods devised in various ways, which include this mixing, have also been proposed.
For example, PWM (pulse width modulation) pulses are used as ON pulses, and components with a frequency higher than that of the low-frequency rectangular pulses are mixed therewith, and the pulse width is gradually widened from the rise of each pulse at the start of each ON pulse. Then, the pulse concerned is changed so that the pulse width thereof can be gradually made narrower as the pulse orbit thereof is passing through a half of the predetermined pulse width and approaching the drop portion. In such a way, a waveform approximate to sine waves is obtained, and a feeling of softness is obtained.
Moreover, as represented by the low-frequency therapy device, the electrical living body stimulation device is mainly used for stimulation of a surface muscle called an outer muscle. However, for stimulation of an inner muscle (deep muscle) present largely in a deep portion of the living body, no effective method has been proposed. If the interval between the electrodes is set as narrow as possible and the applied voltage is increased, then it is also possible to give a stimulus that reaches the inner muscle to a certain extent. However, there are limitations on the size of the applied voltage because the living body stimulation is intensified and because such a problem as skin burn also occurs. Therefore, using this method of increased voltage is not realistic. As a method for solving these problems, there is also proposed a method of giving the stimulus to the deep muscle using high-frequency pulses by superimposing the high-frequency pulses on the low-frequency pulses.
However, in this method, though such high-frequency components reach the deep muscle, a stimulation feeling occurs at the time of the rise of the low-frequency rectangular pulses since a waveform created by superimposition of the low-frequency rectangular pulses and the high-frequency pulses is used. That is to say, owing to the stimulation feeling like prickling (or sticking, shaking), long-time use and daily positive use of the device are hindered.